/*
 * Copyright 2020 lcnap
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package pers.lcnap.simplerpc.rpc.handler.codec;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import pers.lcnap.RpcResponse;
import pers.lcnap.simplerpc.util.KryoUtil;

import java.util.List;

/**
 * {@link RpcResponse} 的解码器。
 * {@link RpcRequestToByteEncoder} 编码器。
 *
 * @see State
 */
public class ByteToRpcResponseDecoder extends ByteToMessageDecoder {

    private State state = State.Header;

    private int bodyLen;

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        switch (state) {
            case Body:
                if (in.readableBytes() < bodyLen) {
                    return;
                }
                ByteBuf byteBuf = in.readBytes(bodyLen);
                RpcResponse response = KryoUtil.read(byteBuf);
                out.add(response);
                state = State.Header;
                byteBuf.release();
                break;
            case Header:
                if (in.readableBytes() < 4)
                    return;
                bodyLen = in.readInt();
                state = State.Body;
                break;
        }
    }
}
